[Freeswitch-users] Need help cc Gateway (SIP trunk) setup for provider using Auth ID

My SIP provider uses - User ID (same as Caller ID Number) - Password - Auth ID (different from User ID) for registration. I have to admit that I'm completely at loss on how to configure freeSWITCH using Auth ID. I tried all combinations I could think off but I just keep getting 403 error messages. Help is very much appreciated.